Siemens SINAMICS S120 Commissioning Manual page 228

Commissioning
5.7 Basic parameterization of the drive objects
Parameterizing the load gearbox position tracking
If you have parameterized encoder 1 for the position control, you can set the position tracking
as follows:
1. Activate the "Activate load gearbox position tracking" (p2729.0) option.
2. Activate the desired axis type (p2720.1).
By default, the "Rotary axis" axis type is active.
3. If required, correct the number of resolvable revolutions for a rotary absolute encoder in the
"Virtual revolutions" (p2721) field.
4. If required, correct the value for the tolerance window for the position tracking in the
"Position tracking tolerance window" (p2722) field. The value is specified in whole encoder
pulses.
Examples of LU configurations
The unit LU is a free dimension, independent of SI units, for the position control of an EPOS axis.
The LU per load revolution upper limit is limited by the encoder resolution (rXXXX). A value
above this limit can be selected, but then not all set positions can be approached because they
may be between two encoder lines. This could result in an unsmooth axis.
The LU per load revolution should be selected as high as possible. In this way, a better dynamic
response can be achieved. If the values for p2506 are too low, this can result in jumps when
speed precontrol is activated.
For good repeat accuracy, the LU per load resolution should be selected in the ratio of 1:10 to
the encoder resolution, if the encoder supports this resolution at the required dynamic response.
Example 1: Linear axis – spindle (encoder on the motor side)
Leadscrew pitch = 10 mm
Gear ratio i = 1 (p2505 / p2504)
Target variable to be controlled: mm
Encoder resolution = 15,000 LU
10 mm distance are travelled per load revolution. According to the encoder resolution,
maximum 15,000 LU/10 mm = 1,500 LU/mm can be defined. We will select 1,000 LU per mm
(1 LU = 1 µm). 10 mm per revolution results in 10,000 per revolution:
• p2506 = 10,000 LU per load revolution
Example 2: Rotary axis (encoder on the motor side)
Gear ratio i = 44.5
• p2504 = 445 motor revolutions
• p2505 = 10 load revolutions
Target variable to be controlled: ° (degrees)
Encoder resolution = 364,544 LU
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Commissioning with Startdrive
Commissioning Manual, 06/2020, 6SL3097-5AA10-0BP2